An antenna is an array of conductors (elements), electrically connected to the receiver or transmitter used for sending/receiving radio waves. Antennas can be made to transmit and receive radio waves in all horizontal directions equally, or preferentially in a particular direction.
An antenna may include parasitic elements, parabolic reflectors or horns. It can also serve to direct the radio waves into a beam or other desired radiation pattern. Older phones used external antennas while most current phones use an internal antenna. The size and shape of the antenna is designed according to the type of radio waves being used.